[2.6] Remove possible call_user_func()

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Remove possible call_user_func() introduced in 2.6
no they cannot. See the typehint on setNormalizer, and the detection of lazy options. Both are enforcing the usage of a Closure